1. Field of the Invention
The present invention relates to a power supply apparatus and a power supply controlling method for use with a multi-function type electronic device that operates as a portable telephone, a GPS (Global Positioning System), and a music program reproducing player.
2. Description of the Related Art
There are many types of portable information terminal units referred to as PDA (Personal Digital Assistant) units. As PDA units, cellular type portable telephone units, simple type portable telephone units (for example, PHS: Personal Handy phone System units), portable personal computers and electronic handy note books are known. When a portable telephone is connected to a portable personal computer, an electronic mail can be sent and received. As other examples of PDA units, GPS terminal units and portable music program reproducing players are known. A GPS terminal unit detects signals from satellites and displays the current position of the unit on its display. A portable music program reproducing unit downloads a music program to a record memory that is attachable thereto and detachable therefrom and reproduces the downloaded music program.
As such various types of PDA units are becoming common, there may be many situations of which the user should carry them at a time.
To solve such inconvenient situations, multi-function type PDA units have been proposed. For example, a multi-function type portable information terminal unit having a portable telephone function (a conventional cellular telephone function or a PHS function), a GPS function for locating the current position, and a music program reproducing function for reproducing a downloaded music program has been proposed. With such a multi-function type portable information terminal unit, the user can conveniently and easily use such functions.
However, such a multi-function type portable information terminal unit has only one battery that supplies an electric power to a plurality of functional portions. Thus, when the user uses one function of the unit, if the power of the battery is consumed, the user cannot use another function.
For example, after the user has enjoyed a music program with the player function of the multiple-function type portable information terminal unit that has the telephone function, the GPS function, and the player function, when the user wants to use the telephone function, if the battery has been exhausted, the user cannot use the telephone function because sufficient power cannot be supplied. Thus, unless the user always checks for the remaining battery capacity, he or she may not use his or her desired function.